Field of the Invention
The present invention relates to a method for regulating the speed of a clamping and lifting apparatus.
Brief Description of the Related Art
It is a known approach to use clamping and lifting apparatus on single-rope and multi-rope Koepe hoisting installations. Such an apparatus can simultaneously clamp and hold, lift or lower all ropes of a cageway without complex preparations. Hydraulically operated clamping cylinders open and close the clamps to such a degree that initial clamping is achieved securely. The clamping devices are arranged on two clamping bars, the lower one of which is configured to be stationary and the upper one of which is configured to be mobile. The upper clamping bar is moved by means of lifting cylinders and is thus responsible for lifting and lowering the ropes. During the idle strokes of the upper clamping bar, the ropes are supported in the lower clamping bar, in contrast.
In the state of the art so far, the hydraulic oil feed and discharge of the master lifting cylinder is controlled by a valve activated with a permanently preset voltage value (0-10 V corresponding to the valve deflection 0-100%). The other lifting cylinders are guided with a position-based slave regulation. The fed and discharged volume flow of the hydraulic oil is controlled thereby. Since the fed and discharged volume flow is dependent on the load, however, it is not possible in the hitherto state of the art to directly specify how fast the clamping and lifting apparatus is actually moving and whether a sufficient amount of hydraulic oil can be replenished in the individual lifting cylinders. When the load direction is opposite to gravity (load towards the top) for example, the speed of the lifting cylinders is too high, since the load presses the hydraulic oil out of the upper side of the lifting cylinder too fast. Since the permanently preset voltage value which is based on a load-free case for controlling the valve cannot be adjusted variably, the pumps cannot replenish sufficient hydraulic oil on the lower side of the lifting cylinder, since these are configured only for the required amount of hydraulic oil for the projected speed of the lifting cylinders. When the volume of hydraulic oil required in the lifting cylinder chambers exceeds the volume actually provided by the pumps, the pressure in the lifting cylinder chambers breaks down, and, in dependence on whether the journey is upward or downward with load, a vacuum is formed in the corresponding cylinder chamber. The consequence is that the configuration so far contributes to operating the clamping and lifting apparatus on single-rope and multi-rope Koepe hoisting installations in critical operational states. Further, the configuration so far does not offer the possibility of recognizing occurring failures at an early stage, and of initiating corresponding counter-measures before critical operational states can actually occur.